Carrier system



Oct. 17, 1933. w HALSTEAD, JR 1,931,071

CARRIER SYSTEM Filed July 26, 1932 2 Sheets-Sheet 1 W K O /7 #1 2 2a O M 22 A? /4 Inventor": George W. Halstead Jrz,

His Attorney.

Wald- 2 Sheets-Sheet 2 G. W. HALSTEAD, JR

CARRIER SYSTEM Filed July 26, 1932 Oct. 17, 1933.

George W. Halstead .Jn,

-HiS Attorney.

Patented Oct. 17, 1933 UNITED STATES oanama SYSTEM George W. Halstead, In, Columbus, Ohio, assignor to General Electric Company, a corporation of New York Application July 26, 1932. Serial No. 624,741

12 Claims.

My invention relates to carrier systems, wherein a carrier is adapted to be set in operation, as

for example at a loading station, and there after travel to another station, such, as an un- 6 loading station, where it is automatically reversed and brought back to the loading station.

More specifically, my invention provides improved accuracy in the control of traveling bucket storage equipments of the type operated by means of a single cable which serves both for the hoisting and for the horizontal travel of the bucket or carrier. Each end of the cable is wound about a hoisting drum while a loop in the cable, suitably supported from pulleys, serves for the support of a bucket or material carrier. The drums are, therefore, rotated in the same direction during the raising or lowering of the bucket. The horizontal travel of the bucket is accomplished by connecting a trolley motor by means of a clutch to one of the hoisting drums and through a differential to the other hoisting drum so that the trolley motor drives the drum in opposite directions.

,If the single cable drive is to be operated automatically both hoisting and trolley limit switches are, necessary to control thmenergization of the respective motors. The hoisting limit switch can be directly connected to the hoisting motor. If the trolley limit switch is connecteddirectly to 30 the trolley motor, however, any slippage whatever of the clutch causes inaccuracies in the stopping of the bucket. Inasmuth as this slippage is accumulative, it will be seen that after a number of operations the bucket might be brought to a standstill some distance from the unloading station. 1

In carrying out my invention in one form thereof, I provide means responsive only to opposite movements of the hoisting drums for oper- 40 ating a trolley limit switch. More specifically, I provide a second differential the bevel gears of which are respectively arranged to be driven from the hoisting drums, so that whenthe hoisting drums are rotated in the same direction the bevel gears are rotated in opposite directions. Consequently,'by gearing the trolley limit switch to the ring gear of the diflerential this switch is not operated during the hoisting operations, but

as soon as the drums rotate in opposite direc-' tions the bevel gears are rotated in the same direction thereby causing the ring gear'to operate the trolley-limit switch-in direct proportion to the horizontal travel of the bucket.

For a more complete understanding of my invention, reference should now be had to the drawings in which Fig. 1 illustrates diagrammatically my invention applied to a material carrying system; Fig. 2 is a perspective view, partly in section, of an adjustable limitswitch used for the selection of a particular silo which is to be 60. filled, while Fig. 3 diagrammatically illustrates a suitable control system as applied to the apparatus shown in Fig. 1.

Referring now to Fig. 1, I have shown my invention in one form as applied to the control of a hoisting motor 10 and of a trolley motor 11, which motors serve to drive a material carrying bucket 12 through a predetermined cycle of operations. The bucket 12 is supported by a loop 13 in a supporting cable 14. By means of the cable 14 the bucket is raised and lowered as well as moved in a horizontal direction. It will be ob- -served that one end of the, cable is wound about a hoisting drum 15, the cable extending from the I drum over pulley 16, round pulley 17, over the 76- pulley 18 supported in a carriage 20 and to the bucket 12. The other end of the cable is wound about a hoisting drum 21 and extends from the drum over a pulley 22, about a pulley 23, and over a pulley 24 supported from the carriage 20 to the bucket 12. The carriage 20 is supported from a track or I-beam 25 which track extends over the silos or unloading stations 1L, IR. and 2B. A loading station, commonly called the pit, is indicated at 26. I

It will be observed that the'hoisting motor 10, by means of a bevel gear 30, is geared to a ring gear 31 of a differential mechanism 32. The

hoisting drum 15 iscdnnected by means of the shaft 33 to the bevel gear 34 of the differential 00 mechanism while the shaft 35 serves to connect the hoisting drum 21 to the bevel gear as of the diiferential. The hoist limit switch 38 isseared to the hoisting motor 10 and serves, as a part of its function, to control the energization of the 9 hoisting motor. An electrically operatedclutch 40 serves to connect and disconnect the trolley motor 11 from the hoisting drum 21. As shown, this clutch is in its disengaged position and if the hoisting motor 10 is energized it will be seen that the hoisting drums 15 and 21 are rotated in the same direction, so that the cable 14 is either wound on the drums, thereby causing the loop 13 to shorten and the bucket .12 to raise, or the cable may be unwound, thereby lengthening the loop 13 and causing the bucket 12 to be lowered. Assuming that the bucket 12 is in the position shown and it is desired to move the bucket to the left, the clutch 40 is operated to connect the energization of the trolley motor.

switch forms no part of the present invention.

trolley motor 11 to the drum 21 and this motor is energized in a direction to rotate the drum 21 in a direction to unwind the cable therefrom. At the same time the drum 15 is driven in a direction to wind up the cable inasmuch as the direction of rotation of the trolley motor 11 is reversed by means of the differential 32.

The trolley limit switch 42', which serves as a part of its function to control the energization of the trolley motor 11, is geared to the drums 15 and 21 by means of a differential mechanism 43. Inasmuch as the trolley limit switch is to be operated whenever the bucket moves in a horizontal direction, the bevel gears 44 and 45 are arranged to be driven in opposite directions whenever the hoisting drums 15 and 21 are rotating in the same direction. This is accomplished by directly connecting the bevel gear 44 by means of a sprocket gear 46, a sprocket chain 47, and a sprocket gear 48 secured to the shaft 33; The bevel gear 45 is driven by means of a sprocket gear 49 secured to the shaft 35, sprocket chain 50, a sprocket gear 51, and by gears 52 and 53. The provision of the gears 52 and the gear 53 secured to the bevel gear 45 causes the bevel gear to be rotated in one direction whenever the bevel gear 44 is rotated in the opposite direction. As soon, however, as drums 15 and 21 are rotated in opposite directions, it will be observed that the bevel gears 44 and Y45 are rotated in the same direction thereby imparting rotation to the ring gear 55 of the diiferential mechanism 43, and by means of the gear 56 the operation of the trolley limit switch is accomplished.

As I have stated, if the trolleylimitswitch had been connected to the trolley motor any slippage of the clutch would have introduced an error in bringing the bucket 12 to a standstill. By connecting the trolley limit switch through a diiferential, however, inaccuracies of stopping have been. substantially, if not entirely, eliminated.

Referring now to Fig. 2, I have shown one form of a limit switch which is suitable for the selection of the desired silo, as well as for the control of the This limit It is fully described and broadly claimed in application Serial No. 588,368, filed January 23, 1932 by Clydev H. Freese, entitled Carrier system" and assigned to the same assignee as the present invention and-which application also describes and claims a control system for carriers. I therefore do net herein claim anything shown or described in sa d Freese application which is to be regarded as prior art with respect to this present application. Briefly, this limit switch may be described in the present application by stating that the trolley limit switch 42 consists of six lug carrying disks 61', 62, 63, 64, 65 and 66. Each disk, as for example the disk 61, is provided with holes 6'7 distributed about its periphery so that the lugs 68, 69 and 70 secured thereto may be adjusted to any desired angular position. The lug 68 serves to close contacts '71 whenever this lug engages the-small -metal wheel 72 carried on the lower part of the armature '73 of the switch 71. A compression upwardly by compression spring '79 so that as soon as the contacts '71 are closed the member 77 engages the notched lower end 80 ofthe armature 73. The contacts may be opened by the lug 69 or the lug 7 0 engaging a wheel 82 carried by the member 77. The result of the lug striking the wheel 82 is to cause'the member 77 to be pushed out of engagement with the lower end 80 so that the compression spring 74 opens the contacts. It will be understood, of course, that the remaining contacts are similarly opened and operated.

The selection of a'silo into which coal or like material is to be carried is accomplished by the adjustment of the relative angular positions of the disks 61, 62 and 63' with respect to the disks 64, 65 and 66. The latter disks serve to stop the trolley motor of the bucket whenever it reaches the position over the loading station while the loading contacts serve to stop the bucket over a selected silo. These contacts 64, 65 and 66 are driven by bevel gear 56 while the adjustable contacts 61 62 and 63 are driven by the meshing gears 84, 85, 86 and 87. Independent rotation from a housing 90, to which rod and housing are respectively secured the gears and 86. An outwardly flaring flange 91 of the housing provides a convenient means of rotating the housing and in conjunction with a pointer 92 forms an indicating disk which may be calibrated for the respective silos. For example, the indicator 92, as shown, points to 2L meaning the second left-hand silo. If the wedge 88 were released and the flange 91 rotated until 1R occupied a position opposite the indicator 92, the selection of the first right-hand silo would have been accomplished.

The hoisting limit switch 38 is provided with a plurality of normally open and normally closed contacts of the same general design as the trolley limit switch 42. a

It is believed that a thorough understanding of the arrangement and operation of the various parts of a suitable control system will best be understood from a complete description of the operation of the system as a whole and, therefore, the construction and arrangement of certain typical devices only will be first described in detail. As shown in Fig. 3, the hoisting motor 10 and the trolley motor 11 are of the alternating current type. The direction of rotation of the hoisting motor 10 is controlled by means of the direction switches 98 and 99, while the direction switches 100 and 101 control the directionof rotation of the trolley motor 11. A slack cableswitch 102 is arranged to open a pair of contacts 103 and to close a pair of contacts 104 whenever the bucket irrespective of power failure. These switches are similarly constructed; for example, the switch 105 is arranged to be latched into position by means of a member 110 engaging a shoulder-111";-

provided on the armature of the sequence relay 105. A trip coil 112 is arranged to release the latching member 110 from engagement with the shoulder 111 so that the relay 105 may be operated to its unlatched position. A timing relay 113 is provided with a time delay device 114 so that the time ,of closing of this relay may be adjusted as desired. Additional timing relays 115 and 116 are respectively provided with short circuited windings 117 and 118-which serve to introduce a time interval before these relays close their contacts.

It is now believed that a comprehensive understanding of the invention, including the construction and arrangement of the various apparatus, as well as its operation, will be facilitated by a description or the operation of the system as a whole.

In the operation 01' my invention in the form shown it will be assumed that the bucket 12 has been lowered to the loading station or pit 26 and it is desired to drive the bucket 12 continuously from the loading station to and from the first right-hand silo or unloading station. Consequently, the wedge 88 is moved away from the housing 90 until the flange91 is rotated into the position which brings the indicia 1R into coincidence with the pointer 92. The line switches L1 and L2 are then closed to energize the supply lines 120 and 121. An energizing circuit may be immediately traced from the supply line 120 for the operating coil 122 of the sequence relay 106. This circuit may be traced from supply line 120 by conductor 123, contacts 124 of the sequence relay 105, conductors 125 and 126, contacts 127 of the sequence relay 107, conductors 128 and 129, non-adjustable trolley limit switch'contacts 64, conductor 130, operating coil 122 and by conductors 131 and 132 to the other supply line 121. The sequence relay 106 will thereupon be operated to its latched-in position with its contacts 133 and 134 and 135 closed, and its contacts 136, 137' and 138 opened. As soon as the contacts 133 are closed the time relay 113 is energized through a circuit which may be traced from the supply line 120 by conductor 123, contacts124 of the sequence relay 105, conductor140, hoisting limit switch contacts 141, contacts 133 o! the sequence relay 106, operating coil 142 01 thetiming relay 113 and by conductor 132 to the other supply line 121. At the same time the sequence relay 108 is operated to its latched-in position by reason of an energizing circuit which maybe traced from the supply line 120 by conductor 123, contacts 124 of sequence relay 105, conductor 140, hoisting limit switch contacts 141, contacts 133 of sequence relay 106, conductor 144, operating coil 145 of the sequence relay 108 and by conductors 146 and 147 to the other supply line 121.

The timing relay 113by reason of the timing device 114 does not immediately close its contacts and by thus introducing a time interval permits the loading of the bucket 12 with coal or the like before it is hoisted from the loading station. As soon as this relay closes its contacts, however, the sequence relay 107 ismperateddnto its latched-in position by reason of an energizing circuit which may be traced from the supply line 120 by conductor 123, contacts 124 of the se quence relay 105, conductor 140, hoisting limit switch contacts 141, contacts 133 of the sequence relay 106, conductor 144, contacts 150 of the timing relay 113, operating coil 151 of the sequence relay 107 and by conductors 152'and 132 to the other supply line 121.

The closing of the contacts 154 of the sequence relay 107 serves toenergize the hoisting direction switch 98 of the hoisting motor 10 through a circuit which may .be traced from the supply line 120, by conductor'123, contacts 124 of sequence relay 105, conductor 125, hoisting limit switch contacts 155, conductor 156, contacts 154 oi the "sequence relay 107, conductor 157, operating coil of the hoisting relay 98, interlock contacts 160 of lower direction switch 99 and by conductor 161 to the other supply line 121.

Consequent to the closing of the hoisting direc.

The hoisting relay 115 is operated to open its contacts 162 and 163 as soon as the hoisting direction switch 98 closes by reason of the closing 01 the contacts 164 operated with this direction switch,, This circuit may be traced from the supply line120'by conductor 165, operating coil oi the hoisting relay 115, conductor 166, contacts 164 and by conductor 167 to the other supply line 121. The function of the hoisting relay 115 is to introduce a time interval before the trolley motion of the bucket can be initiated.

As soon as the bucket 12 reaches the trolleying position above the silos the hoisting limit switch contacts 141 and 155 are operated to their open positions while the hoisting limit switch contacts a 170 and 171 are closed. The hoisting direction switch 98 is thereby deenergized so that the bucket 12 immediately comes to a standstill. The contacts 164 of the hoisting direction switch 98. are opened to interrupt the energizing circuit of the hoisting relay 115, which relay closes after a predetermined interval. The hoisting limit switch contacts 170 partially complete an ener-' gizing circuit for the sequence relay 105. This circuit is completed as soon as the hoisting relay 115 closes its contacts 163. Assuming that the time interval has expired and that the contacts 163 are closed, the energizing circuit for the sequence relay 105 may be traced from the supply line 120 by conductor 172, hoisting limit switch contacts 170, conductor 173, operating coil 174 of the sequence relay'105, conductor 175, contacts 176 of the sequence relay 107, conductor 178, contacts 163 of the timing relay and by conductor 177 to the other supply line 121. The sequence relay 105 is thereupon operated to its latched-in 115 position with its contacts 124 and 178 open and.

its contacts 179, 180 and 181 closed.

The opening of the contacts 178 of the sequence relay 105 reenergizes the clutch releasing coil 185, while the contacts 179' or the relay 105 completes an energizing circuit for the clutch engaging coil 186. -This energizing circuit may be traced from the supply line 120 by conductor 187, contacts 179 of the sequence relay 105, conductor 188, the clutch engaging coil 186 and by conductors 189 and 190 to the other supply line 121. The clutch 40 is thereby operated to connect the trolley motor 11 to the hoisting drum 21.

Inasmuch as the bucket is to be driven to ther right-hand silo, the switch 191 is'pperated to its right-handposition, The direction switch 101 of the trolley motor 11 is now closed, so that the trolley motor is energized in a direction todrive the bucket towards the rightahand silo, by means of an energizing circuit which may be traced from the supply line 120 by conductor 172, hoisting limit switch contacts 170, conductor 173, contacts 180 of the switch relay 105, adjustable trolley 1 limit switch contacts 63, contacts 192 oi the sequence relay 108, conductor 193, contacts 194 of sequence relay 109, conductor 195, reversing switch 191, conductor 196, operating coil or the direction switch 101 and by conductor 197 to the other supply line 121'.

The time closing. relay 115 is energized to open bucket 12 in position for lowering into the silo. At the same time the contacts 198 are opened to deenergize the time closing relay 115. The closing of the trolley limit switch contacts 62 com- .pletes an energizing circuit for the trip coil 202 of the sequence relay 107. This circuit may be traced from the supply line 120 by conductor 203, trolley limit switch contacts 62, conductor 203, contacts 204 of the sequence relay 108, conductor 205, contacts 206 of thesequence relay 107, trip 0011202 and by'conductor 147 to the other supply line 121. The sequence relay 107 is, therefore, operated to its unlatched position to close its contacts 207 thereby completing energizing circuit for the trip coil 208 of the. sequence relay 108. This circuitmay be traced from the supply line 120 by conductor 203, trolley limit switch contacts 62, conductor 203, contactsJ204 of the sequence relay 108, conductors 205 and 209, trip coil 208, contacts 210 of the sequence relay 108, conductor 211, contacts 207 of the sequence relay 107 and by conductor 147 to the other supply line 121.

It will be assumed that the time closing relay 115 has closed its contacts 162 and 163. An energizing circuit for the trip coil 112 ofthe sequence relay 105 may now be traced from the supply line 120 by conductor 172, hoisting limit switch contacts 170, conductor 173, contacts 181 of the sequence relay,105, trip coil 112, conductor 215, contacts 216 of the sequence relay 107, contacts 162 of the hoisting relay 115 and by conductors 217 and 177 to the other supply line 121.

The sequence relay, 105 is immediately operated to its unlatched position, thereby interrupting by means of its contacts 179 the circuit to the clutch engaging coil 186 while the clutch releasing coil 185 is energized through the contacts 178 operated with the sequence relay 105. The clutch 40 is thereupon operated to disengage the trolley motor from the hoisting drum 21. The contacts g 124 of .the sequence relay 105- are closed as this relay is unlatched and completes an energizing circuit for the trip coil 218 of the sequence relay 106. This circuit may be traced from the supply line 120 by conductor 123, contacts 124 of the sequence relay 105, conductors 125 and 126, contacts-127 of the sequence relay 107, conductors 128 and 219, trolley limit switch contacts 61, conductor 220, contacts 134 of the sequence relay 106, trip coil 218 and by conductors 221 and 132 to the other supply line 121.

As soon as this relay 106 is unlatched the equipment is in readiness for thebucket 12 to be lowered into the silo. An energizing circuit may be traced for the lower-direction switch 99 of the hoisting motor 10 from the supply line 120 by conductor 123, contacts 124 of the sequence relay 105, conductors 125 and 126, contacts 127 of the sequence relay 107, conductors 128 and 216, contacts 137 of the sequence relay 106, conductor 217, contacts 103 of the slack cable switch 102, conductor 217', operating coil-of the lowering di-.

rection switch 99 and by conductor 217" to the thereupon energized in a direction to'lower the bucket 12 into the silo. As .the bucket descends into the silo the hoisting limit switch contacts 155 are closed.

As soon as the bucket strikes the coal or other material which is being carried to the silo, the, tension is removed from the supporting cable and the slack cable switch 102 operates to open its contacts .103 and to close its contacts 104., Of course, the lowering direction switch 99 is immediately deenergized as soon as the contacts 103 are opened andthe hoisting circuits are established by the closing of the slack cable switch contacts 104 which contacts complete energizing circuits for the sequence relays 107 and 109. The energizing circuit for. the sequence relay 109 may be traced from the supply line 120 by conductor 123, contacts 124 of the sequence relay 105, conductors 125, 225, contacts 138 of the sequence relay 106, conductor 226, contacts 104 of the slack cable limit switch 102, conductor 227, operating coil 228 of the sequence relay 109 and-by conductors 229, 230 and 132 to the other supply line 121. The energizing circuit for the sequence relay 107 is derived from the conductor 227 forming a part of the energizing circuit for the sequence relay 109' and may be traced from, the conductor 227 by conductor 231, contacts 136 of the sequence relay 106, conductor 232, operating coil 1510f the sequence relay 107 and by conductors 152- and 132--,to the other supply line 121. These sequence relays are immediately operated to their latched-in positions. Consequently the energizing .circuit may now be traced for the operating coil of the hoisting direction switch 98 from the supply line 120 by conductor 123, 0011- Y tacts 124 of the sequence relay 105, conductor 125, hoisting limit switch contacts 155, conductor 156, contacts 154 of the sequence relay 107, conductor 157, operating coil of the hoisting direction switch, contacts 160 of the lowering direction switch 99 and by conductor 161 to the other supply line 121. Consequent to the closing of the hoisting direction switch 98, the hoisting motor 10 is energized in a direction to hoist the carrier or bucket 12 from the silo 1R. The closing of thecontacts 164 operated with the hoisting direction switch again serves to complete the energizing circuit for the time closing relay 115 which, relay immediately opens its contacts. s

As the bucket reaches its trolleying position above the silos the hoisting limit switch contacts are opened to deenei'gize the hoisting direction switch 98. The hoisting limit switch contacts 141 are also opened while the hoisting limit switch contacts and 171 are closed. The time closing relay 115 after a predetermined time interval closes its contacts 163 to complete an energizing circuit for the operating coil 174 of the sequence relay 105. This sequence relay is immediately operated to its latched-in posi tion to complete the energizing circuit for the clutch engaging coil '186.- The closing-of the contacts of this sequence relay completes an energizing circuit for the operating coil of the direction switch 100, which circuit may be traced from the supply line 120 by conductor 172, hoisting limit switch contacts 170, conductor 173, contacts 180, trolley limit switch-contacts 66, con-, ductor 235, contacts 236 of the sequence relay 108, conductor 237, contacts 238 of the sequence relay 109, conductor 239, reversing switch 191, conductor 240, and 240', operating coil of the direction switch 100 and by conductor 241 to the- 1,081,071 &

for the time closing relay 115.

The bucket 12 is brought to a standstill over the loading station by the opening of the trolley limit switch contacts 66 which deenergize the direction switch 100. At the same time the trolley limit switch contacts 64 and 65 are operated to their closed positions. .The closing of the trolley limit switch contacts 65 completesan energizing circuit for the trip coil 202 of the sequence relay 107. This circuit may be traced from the supply line 120 by conductor 243, trolley limit switch contacts 65, conductor 244, contacts 245 of the sequence relay 108, conductors 209 and 205, contacts 206 of the sequence relay 107, trip coil 202 and by conductor 147 to the other supply line 121. The sequence relay 109 is also operated to its unlatched position by reason 01' the completion 01' an energizing circuit for its trip coil 248, which circuit may be traced from the supply line 120 by conductor 243, trolley limit switch contacts 65, conductors 244 and 249, contacts 250 of the sequence relay 109, trip coil 248' and by conductor 251 to the other supply line 121.

As'soon as the time closing relay 115 closes its contacts the energizing circuit for the t rip coil 112 is completed and the sequence relay 105 is thereby operated to its unlatched position. The

Est

sequence relay 106 ,is now operated into its latched-in position bythe energizing circuit traced above with this relay. Consequently, an energizing circuit is now completed for the time closing relay 116 which circuit may be traced from the supply line 120 by conductor 123, contacts 124 oi. the sequence relay 105, conductors 125 andi 128, contacts 127 oithe sequence relay 107, conductor 128 hoisting limit switch contacts 171, contacts 135 of the sequence relay'106, conductor 254, operating coil 255 of the relay 116 and by conductors 230 and 132 to the other supply line 121. The interval required for the closing of this relay is introduced in order to give the bucket time to come to a standstill and to eliminate the swinging oi the bucket before it is lowered to the loading station. As soon as this relay 116.

closes the energizing circuit is completed for the lowering direction switch 99. which circuit is derived from the conductor 254, forming a part of the energizing circuit for the operating coil of the relay 116, by conductor 257, contacts of the time closing relay 116, conductors 258 and 217,

coperating coil oi the lowering direction switch 9i! and by conductor 217" to the other supply line 121. The hoisting motor 10 thereby rotates. in a direction to lower the bucket to the loading station. The bucket or carrier is brought to a standstill by the opening of the hoisting limit switch contacts 171 which interrupts the energizing circuit to the lowering direction switch 99; at the same time the hoisting limit switch contacts 170 are opened while the contacts 141 and 155 are closed. v

A completecycle oi operation has now been described and it will, of course, be understood that the carrier may be continuously operated from the loading station to a selected unloading station, and my invention insures the accurate stopping oi the bucket 12 above the loading station or a selectedsilo irrespective of any slippage or the clutch in the troll motor of the hoisting drum.

What I claim as new and desire to secure by Letters Patent oi the United States, is:

1. In combination, a pair of hoisting drums, a trolley motor arranged to drive said drums in opposite directions, a hoisting motor for rotating said drums in the same direction, a trolley limit switch for controlling the energization oi. said trolley motor, and means responsive to the opposite rotation oi said drums for operating said limit switch. v a

2. In combination a traction drive, a cable for supporting and driving a carrier, a pair oi drums around which the ends of said cable are wound, a differential mechanism mechanically connecting said drums, a hoisting motor mechanically connected to said diiierential mechanism for simultaneously rotating said drums in forward or reverse direction, a trolley motor arranged to drive said drums in opposite directions, a limit switch, for controlling the energization of one of said motors, and means responsive only to opposite movements of said drumsior operating said limit switch.

3. A material handling systemhaving a car rier arranged to be operated in a predetermined cycle from a loading station to and from an unloading station comprising a single cable for supporting and imparting translational movement to said carrier, traction drums around which the ends 01' the cable are wound, a differential mechanism mechanically connecting said trac-.

tion drums, a hoisti'ngmotor arranged to drive through said diiierential mechanism said drums in the same directions. a trolley motor arranged to be mechanically connected to. one 01' said traction drums for rotating said end drums in opposite directions, a trolley-limit switch, a second differential mechanism connected to' said limit switch and interposed between said limit switch and said traction drums, and driving connections for said second diiierential mechanism responsive to therotation oi said drums in opposite directions for causing said second diil'erential to operate said limit switch.

4. A material handling system having a carrier arranged to be operated in a predetermined cycle from a loading station-to and from one or a plurality of unloading stations, means for driving said carrier including a pair of cable drums, a trolley limit switch having a plurality oi nonadiustable switches for stopping said carrier over said loading station and a plurality 01' adjustable switches for stopping said carrier over an unloading station, means for changing the time oi operation of said latter switches with respect to said former switches so that any one of said unloading stations may be selected for thecarrying a hoisting motor for simultaneously rotating TIT said drums in forward or reverse direction, a trolley motor for driving one drum in one direction while driving the. other drum in the otherdirection, a trolley limit switch, a clutch for disengaging said trolley motor from said drums, and means responsive to the rotation of said drums in opposite directions for operating said limit switch.

7. An electrically operated carrier system having'a carrier arranged to be operated in a predetermined cycle from a loading station to and from an unloading station, a cable for supporting and imparting translational movement to said carrier, a pair of traction drums around which the ends of the cable are wound, a dif' ferential mechanism mechanically connecting said drums, a hoisting motor for driving said drums-through said differential mechanism in forward and reverse directions, a trolley motor for driving said drums in opposite directions, a clutch for connecting said trolley motor to one of said end drums, hoisting and trolley limit' switches each of which is provided with a plurality of contacts, means responsive to the rotation of said drums in opposite directions for operating said trolley limit switch, and a plurality of control circuits successively completed by said switches, the completion of each of said control circuits being dependent upon the control circuit last established and upon the operation of said switches.

8. A material handling system comprising a pair of drums, motive means for rotating said Patent No. l, 931,071.

drums in the same directions, a second motive means for rotating said drums in opposite directions, means for controlling said second motive means and means responsive to the opposite rotation of saiddrums for operating said motive means controlling means;

9. A material handling system comprising a pair of drums, 'a differential coupling said drums, amotor for driving said drums in opposite directions, av second motor for driving said drums in the same directions, a limit switch for controlling said first motor, and a'differential means for operating said limit switch responsive to opposite rotations of said drums.

10. Amaterial handling system comprising a carriage, a track for said carriage, a pair' of drums, cable means connecting said drums with said carriage, a trolley, a motor for rotating said drums in opposite directions, a limit switch for said motor and differential means for operating said limit switch responsive to the position of said carriage on the track.

11.\A conveyor system comprising at least one loading station and a plurality of unloading stations, a carriage driving means for said carriage, material supporting structure, motive means for hoisting and lowering said structure toward and "away from said carriage, a second motive means for moving said carriage between said loading station and a selected one of said unloading stations and a difierential mechanism for controlling said second motive means, responsive to the location of said carriage.

12. A conveyor system comprising at leas one loading station and a plurality of unloading stations, a carriage, an electric motor for driving CERTIFICATE "OF CORRECTION.

October 17, 1933.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, 7 line 119, for "reenergizes" read deenergizes; and line 148, for "energized"'readenergizing; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed andsealed this 28th day of November}; A. D. 1933.

. (Seal) F. hi. Hopkins Acting Commissioner 'otla'tente. 

